<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>

*,html,body{
          margin: 0;
          padding: 0;
        }
        .box{
          width: 1500px;
          height: 500px;
          background-color: rgb(215, 221, 221);
          margin: 0 auto;
        }
        .left{
          width: 20%;
          height: 200px;
          background-color: chocolate;
          float: left;
        }
        .right{
          width: 200px;
          height: 200px;
          float: right;
          background-color: cornflowerblue;
        }
        .content{
          overflow: hidden;
          height: 400px;
          background-color: darkblue;
        }

    </style>
</head>
<body>


    <div class="box">
        <div class="left">left</div>
        <div class="right">right</div>
        <div class="content">content</div>
      </div>

    <!-- <script>
        // let a=123123
        // alert(a)
    //     var a=10
    // var sum = a-- + --a + a++ + ++a + a++ + ++a + a++;
    //         //10     8     8    10     10   12     12>>13
    //         console.log(sum,a)
    // alert({})
    console.log(String({}))
    </script> -->
</body>
</html>